Abstract

We present a method to systematically locate and extract capacitive and inductive losses in superconductingresonators at microwave frequencies by use of mixed-material, lumped element devices. In these devices, ultra-low loss titanium nitride was progressively replaced with aluminum in the inter-digitated capacitor and meandered inductor elements. By measuring the power dependent loss at 50 mK as the Al/TiN fraction in each element is increased, we find that at low electric field, i.e., in the single photon limit, the loss is two level system in nature and is correlated with the amount of Al capacitance rather than the Alinductance. In the high electric field limit, the remaining loss is linearly related to the product of the Al area times its inductance and is likely due to quasiparticles generated by stray IR radiation. At elevated temperature, additional loss is correlated with the amount of Al in the inductance, with a power independent TiN-Al interface loss term that exponentially decreases as the temperature is reduced. The TiN-Al interface loss is vanishingly small at the 50 mK base temperature.

Received 21 March 2012Accepted 07 June 2012Published online 09 July 2012

Acknowledgments:

The authors gratefully acknowledge the assistance of F. Farhoodi and valuable discussions with J. Gao, R. Simmonds, J. Aumentado, and J. Whittaker. This work was supported by the NIST Quantum Information initiative and in part by DARPA. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressly or implied, of the U.S. Government.